Tunnels

Regarding the tunnels. I was thinking of them more as an alternative escape/food storage facility. But, Slash, you are correct, they can easily turn into death traps. Especially the complex series of tunnels that I was describing. If it's too complex it will inevitabley confuse me causing me to be trapped with or without zombies. So in the interest of my own life, as well as my general laziness I will probably continue with my one short tunnel, whose exit will be thoroughly disguised, and entrance/exit mindfully barricaded. I do like idea of a system of elevated escape routes, but in reality, I am a little scared of heights. So unless I can overcome my fears beforehand, it's best not to tackle psychological issues in the field. Of course, if the tunnel does turn into a zombie entrance, at least it will force them into single-file rank, thus making it easier to dispatch them, eventually causing enough inactive zombie corpses to block the entrance. But that would eventually smell and probably attract more zombies, so it would still be necessary to vacate my carefully constructed fort.

Zombies vs. Ninjas?
I think I'd have to go with ninjas, hands down on this one. The speed, coordination and hands-of-death required to be a ninja make them predisposed to defeating zombies. The only drawback to being a ninja in a zombie invasion is that ninjas are subordinates. They need to have a leader to give orders and coordinate attacks. Thus the leader is a point of weakness. Granted the leader will most likely be protected by his ninjas which should easily fight off a zombie attack. However, if an opposing faction of ninjas rises, this would definitely complicate matters.
But definitely, Ninjas vs. Zombies goes to Ninjas.